| Description: | In the Linux kernel, the following vulnerability has been resolved:
sysv: don't call sb_bread() with pointers_lock held syzbot is
reporting sleep in atomic context in SysV filesystem [1], for
sb_bread() is called with rw_spinlock held. A
"write_lock(&pointers_lock) => read_lock(&pointers_lock) deadlock" bug
and a "sb_bread() with write_lock(&pointers_lock)" bug were introduced
by "Replace BKL for chain locking with sysvfs-private rwlock" in Linux
2.5.12. Then, "[PATCH] err1-40: sysvfs locking fix" in Linux 2.6.8
fixed the former bug by moving pointers_lock lock to the callers, but
instead introduced a "sb_bread() with read_lock(&pointers_lock)" bug
(which made this problem easier to hit). Al Viro suggested that why
not to do like get_branch()/get_block()/ find_shared() in Minix
filesystem does. And doing like that is almost a revert of "[PATCH]
err1-40: sysvfs locking fix" except that get_branch() from with
find_shared() is called without write_lock(&pointers_lock).
|
